A. Field of the Invention
The present invention is related to systems and methods for obtaining information from RFID tags by means RFID readers/writers and more particularly to a communication network for connecting a plurality of RFID readers/writers with a computer at a minimum cost using simplified and low cost RFID readers/writers controlled by one or more concentrators.
B. Description of the Related Art
RFID (radio frequency identification) is a technology that incorporates the use of electromagnetic or electrostatic coupling in the radio frequency (RF) portion of the electromagnetic spectrum to uniquely identify an object, animal, or person. RFID is coming into increasing use in industry as an alternative to the bar code. The advantage of RFID is that it does not require direct contact or line-of-sight scanning. An RFID system consists of three components: an antenna, a transceiver (often combined into one reader) and a transponder (the tag). The antenna uses radio frequency waves to transmit a signal that activates the transponder. When activated, the tag transmits data back to the antenna. The data is used to notify a programmable logic controller that an action should occur. The action could be as simple as raising an access gate or as complicated as interfacing with a database to carry out a monetary transaction.
Information systems using RFID technology for identifying items, require a plurality of RFID Readers/writers in order to read the information that is stored in RFID tags which are attached to a particular material which is mostly a plastic card.
RFID readers/writers work on particular principle and they have some devices along with them in order to read the information stored in the RFID transponder. Transponder is basically the device which stores the information and sends it to the reader via radio waves which is then captured by the reader. It is to be noted that the communication which takes place between the transponder and the RFID reader doesn't require a wire connection.
Precisely, RFID reader/writer comprises a module, a control unit and a coupling element. The module is comprised by the transmitter and the receiver and the coupling unit comprises the antenna. The reader has to perform three functions in order to read the information, namely energizing, demodulating and decoding. Though this process the reader can read the information stored in the RFID.
Although the RFID readers/writers can differ quite considerably in complexity, depending upon the type of tags being supported, generally, the cost, complexity and manageability of the RFID readers/writers have been obstacles to widespread adoption of the technology.
In some applications of RFID technology, it is necessary the implementation of a great number of RFID readers/writers, especially those that require having an RFID reader for reading a specific tag, such as the Item Tracking System disclosed in U.S. patent Ser. No. 11/856,869.
Said patent application, discloses an item tracking system which makes use of a plurality of RFID readers/writers for automatically monitoring the taking and returning operations of items from one or more storage locations inside a working area. Said system employs a RFID reader per item and there can be dozens of items inside a storage location.
A typical RFID reader has an intelligent controller that handles high level protocols (auto report, detection report, programmable options for information formatting and high level electrical interfaces like Ethernet or rs-232).
Since the above referred system uses a great number of RFID readers/writers, it is necessary to install the lowest cost RFID readers/writers available in order to lower the overall price of the system.
In view of the necessity to count with a very low cost RFID reader/writer, applicant developed a low cost RFID readers and a related network for interconnecting said RFID readers/writers by means of one or more intelligent concentrators—for controlling the reading, writing and verification tasks normally addressed by common RFID readers/writers—to a computer or control system. The computer control system communicates with the plurality of RFID reader by means of a low level protocol which requires very few processing power. The commands of said protocol are processed by each concentrator which in turn controls a network of readers/writers. Since applicant's network system can include several concentrators, any protocol command sent by the computer control system can be processed by two or more concentrators at the same time, thus giving the network system of the present invention the capacity to process a single instruction in parallel, raising the reading/writing processing capacity. Furthermore, specific commands can be sent to specific readers/writers or to all of the readers/writers controlled by a concentrator.
U.S. patent application No. 20070156450 discloses “a system and method of remotely monitoring patient health care characteristics. The system utilizes at least two micro-scale to millimeter-scale sensors, a wireless network, a central hub and pre-processing center and a means for notifying a clinician of the remote patient's condition. The system and method includes sensor to sensor coordination, modular-based sensors and processing, and allows a clinician to remotely configure the system”. Although said system and method discloses the use of a central hub and pre-processing center for controlling said plurality of sensors, it doesn't discloses that the sensors may comprise RFID readers/writers nor that the central hub and pre-processing centers have means for controlling the functions of the RFID tags. Furthermore, it is disclosed that “each of the plurality of sensors is configured to continuously communicate with each other and with the central hub; wherein each of the plurality of sensors is autonomous, thereby capable of automatic configuration with the modular sensing system”, which raises the complexity and cost of the network.
U.S. patent application No. 20070096874 of Mravaca, discloses a system and method are provided for interrogating passive radio frequency identification (RFID) transponders located in compartmentalized areas such as on shelves or in other spatially-partitioned storage areas. The system includes a controller and a plurality of minimal function RFID readers coupled to the controller via a network-compatible cable. The controller is configured to address a subset of at least one reader at a time to interrogate the RFID transponders located in at least one of the compartmentalized areas. The readers are each give a physical location and a unique address, through which the controller would know the locations of the RFID transponders being interrogated. The functions disclosed in Mravaca patent application are specifically designed to be used in inventory control systems which require high level functions which require a lot of processing power. Furthermore, Mravaca patent application does not disclose nor suggest the use of a low level protocol for allowing the communication between a central computer with a plurality or writers readers nor the possibility that a protocol command could be directed to a specific reader/writer or to all of the readers/writers of a network. Also, it does not disclose nor suggest that several tasks could be processed at the same time in the way applicant's network system does using two or more concentrators. Furthermore, the minimal function RFID readers disclosed in Mravaca patent application communicate by means of ETHERNET which is not a simple protocol and requires a lot of processing power and software.
The RFID readers/writers used by applicant's system consists of only the essential processing that is required to write a tag, identify a tag and get the information in it. They communicates with a low level protocol which requires low processing power thus reducing the component count and allowing the use of more limited controllers and the use of fast, low cost and high range networks. This helps in reduce cost and size.
Thanks to the use of one or more intelligent concentrators in applicant's network design, it is possible to use simple and low cost RFID readers/writers, since there is no necessity to include in each reader, electronic means for controlling the reading, writing and verification tasks and helps to modularize the network by helping to separate the software development for the control of the concentrators and RFID readers/writers and for the C.P.U.
Furthermore, since the processing work is distributed among several intelligent concentrators related to the reading, writing and verification of each reader, it is optimized the use of each system component.
Finally, applicant's network achieves high processing velocities since it allows to quickly performing RFID reading, writing and verification operations with several RFID readers/writers at the same time.